A steel sheet for hot pressing includes a specific chemical composition and further includes a steel structure in which an area ratio of ferrite in a region ranging from a surface to 100 m in depth is 30% to 90% and an area ratio of pearlite including an average grain diameter of 5 m or more in a region excluding the region ranging from the surface to 100 m in depth is 10% to 70%.

A steel sheet for hot pressing includes a specific chemical composition and further includes a steel structure in which an area ratio of ferrite in a region ranging from a surface to 100 m in depth is 30% to 90% and an area ratio of pearlite including an average grain diameter of 5 m or more in a region excluding the region ranging from the surface to 100 m in depth is 10% to 70%.

The invention relates to a collet chuck for clamping a dental tool, wherein the collet chuck has at least temporarily a mechanical stress applied to it and is made of steel.

The collet chuck according to the invention is characterized in that the steel, at least in a surface layer, has a nitrogen content of at least 0.1 wt %.

Disclosed is a martensitic stainless steel material for a hydrogen gas environment, having a composition consisting of: 0.03 mass %?C?1.20 mass %, Si?1.00 mass %, Mn?1.50 mass %, P?0.060 mass %, S?0.250 mass %, Cu?0.50 mass %, 8.0 mass %?Cr?22.0 mass %, Ni?1.00 mass %, and N?0.40 mass %, and optionally at least one selected from the group consisting of: Mo?3.00 mass %, V?1.50 mass %, Nb?1.00 mass %, Pb?0.30 mass %, and B?0.0500 mass %, with the balance being Fe and inevitable impurities; having: a content of a precipitate of 1.50 mass % or more, a crystal grain size number of prior austenite grains of 2.0 or more, a metal structure including a martensite structure, a tensile strength of 1,800 MPa or less, and satisfying D.sub.H2(0.7)/D.sub.air?0.8.

Provided is a heat treatment furnace used to anneal a workpiece to be heat-treated, including a heating chamber configured to heat the workpiece, a first cooling chamber configured to cool the workpiece having passed through the heating chamber, a second cooling chamber that is located on a downstream side of the first cooling chamber in a conveying direction of the workpiece and that is configured to cool the workpiece having passed through the first cooling chamber, and an atmosphere gas supply device configured to supply, as an in-furnace atmosphere gas, an exothermic converted gas to each of the first cooling chamber and the second cooling chamber, the atmosphere gas supply device selectively supplying a first gas that is an exothermic converted gas and a second gas that is an exothermic converted gas and that has a dew point lower than a dew point of the first gas.

Provided is a heat treatment furnace used to anneal a workpiece to be heat-treated, including a heating chamber configured to heat the workpiece, a first cooling chamber and a second cooling chamber configured to cool the workpiece having passed through the heating chamber, and an atmosphere gas supply device configured to supply, as an in-furnace atmosphere gas, an exothermic converted gas to each of the first cooling chamber and the second cooling chamber, the first cooling chamber having a first cooling state of cooling the workpiece by using a first coolant and a second cooling state of cooling the workpiece by using not the first coolant but a second coolant different from the first coolant, and the second cooling chamber having a similar configuration to the first cooling chamber.

The present invention discloses a steel for bolts, which comprises the following chemical elements in percentage by mass in addition to Fe and inevitable impurities: C: 0.37 to 0.45%; Si: 0.01 to 0.08%; Mn: 0.45 to 0.80%; Cr: 0.90 to 1.30%; Mo: 0.20 to 0.45%; Ni: 0.10 to 0.30%; V: 0.15 to 0.30%; and Al: 0.015 to 0.035%. The present invention further discloses a method for manufacturing the steel for bolts, which comprises the following steps: (1) smelting; (2) casting; (3) rough rolling; (4) high-speed wire rolling; (5) Stelmor controlled cooling; and (6) heat treatment, wherein the holding temperature of spheroidizing heat treatment is 760 to 790? C. and the holding time is 4 to 12 h, followed by a slow cooling process after the holding with a cooling speed of lower than 40? C./h. The drawing area reduction rate of a coil rod is controlled to 5 to 30%. The heating temperature of quenching and tempering heat treatment is 850 to 950? C. The tempering temperature is 500 to 600? C. The steel for bolts disclosed in the present invention has a uniform structure and performance, has low production costs, and has high strength and good delayed fracture resistance.

A pre-alloyed powder includes, in weight percent, carbon from about 0.75 to about 2 percent; manganese from about 0.1 to about 1 percent; silicon from about 0.1 to about 1 percent; chromium from about 3 to about 6 percent; nickel up to about 4 percent; vanadium from about 1 to about 3 percent; molybdenum from about 4 to about 7 percent; tungsten from about 4 to about 7 percent; cobalt from about 4 to about 7 percent; boron up to about 0.1 percent; nitrogen from about 0.001 to about 0.15 percent, aluminum from about 0.001 to about 0.6 percent, copper from about 0.1 to about 1 percent, sulfur up to about 0.3 percent, phosphorus up to about 0.3 percent, up to about 5 percent total of tantalum, titanium, hafnium and zirconium; iron from about 65 to about 80 percent; and incidental impurities.

In the present disclosure, a motor core can be degreased prior to straightening annealing without a heating device or a vacuum device dedicated to degreasing being provided. A heat treatment furnace according to an embodiment of the present disclosure includes a degreasing chamber for degreasing a motor core, a heating chamber with which the degreasing chamber directly communicates and which is configured to anneal the motor core that has passed through the degreasing chamber, by using a converted gas generated by a converted gas generation device, as an in-furnace atmosphere gas, and a gas flow formation section GF configured in such a manner that the converted gas in the heating chamber flows toward the degreasing chamber.

A bushingless track pin is disclosed. The track pin includes a hardened outer layer and a relatively softer inner core. The track pin may be formed using high carbon steel, which in some cases may be substantially spheroidal martensite crystal structure. A track pin may be formed using the high carbon steel, followed by a hardening process. In some examples, an optional induction hardening process may thereafter be performed on the inner surface most proximal to the central hole of the track pin if needed. The hardening on the inner surface may harden the outer portion while tempering the core portion of the track pin.